In the field of tissue products, tissues have long been made using a process known as “wet pressing”, which refers to the manner in which the newly-formed tissue wet tissue web is mechanically dewatered prior to final drying. More specifically, the wet web, while in contact with a papermaking felt, is pressed against and transferred to a hot drying cylinder, known as a Yankee dryer. During the pressing step, free water within the wet web is expressed and absorbed by the felt. The tissue is then final dried on the Yankee dryer and creped to soften the resulting tissue sheet. While this process is effective, the wet compression of the web prior to final drying densifies the sheet and is therefore detrimental to the ultimate softness and bulk properties of the final product.
More recently, throughdrying has become a popular method of drying tissue webs. Throughdrying avoids the extreme level of compaction associated with wet pressing and relies on hot air passing through the wet web to accomplish drying. Throughdried sheets are inherently less dense (greater bulk) than wet-pressed sheets and are therefore softer. While the ultimate product properties are desirable, throughdrying is more energy intensive and therefore more expensive to operate. Also, there are a great number of existing wet pressing tissue machines in operation and converting them to throughdrying entails a high capital expense, which may not be feasible.
Therefore there is a need for wet-pressed tissue products, particularly single-ply wet-pressed tissue products, that exhibit a level of softness previously associated with throughdried tissues.